Regions Of Turbulent Kinetic Energy Research Articles

Numerical investigation of bimodal tip clearance effect on the lift-drag and flow characteristics of a hydrofoil

Tip leakage flow has adverse effect on energy conversion of the hydraulic machinery. The new tip clearance structure based on Bimodal Gaussian function is designed to reduce tip leakage vortex. The effects of bimodal structure with different amplitudes and arrangement positions on lift-drag and flow characteristics are studied. The results show that the maximum rise of the lift-drag ratio reaches 5.88% when the bimodal structure amplitude is equal to the tip clearance size. The bimodal structure reduces the outflow velocity at the peak and forms a smooth streamline, which weakens the entrainment with the mainstream. The location of the bimodal structure far away from leading edge helps to produce smooth streamlines and make the flow field smoother, and reduces the area of high turbulent kinetic energy region near leading edge and in tip clearance outflow region significantly. The arrangement position of bimodal structure close to leading edge can produce a low-speed zone or a recirculation zone in the mainstream, which can block the mainstream flow and reduce the energy characteristics of the hydrofoil.

The influence mechanism of the submerged dikes on the three-dimensional hydrodynamic characteristics at the 90° confluence

The confluence area serves as the pivotal control unit in natural rivers, and the implementation of spur dikes at the confluence enables regulation of flow patterns, influences pollutant mixing, and safeguards against river scouring. This study establishes a three-dimensional hydrodynamic model for the 90° confluence with dikes, aiming to explore the impact of the number, angle, and spacing of the dikes on hydrodynamic characteristics at 90° confluence. The results show that (i) the closer the spacing between the dikes, the wider the range of low water level area upstream becomes. An increased number of dikes makes it easier for the downstream water level to recover. (ii) The area of the high turbulent kinetic energy region increases with the increase in the number of dikes. Among the three angle deployments, the dike deployment angle of 60° corresponds to the largest area of high turbulent kinetic energy. When the spacing between dikes is 0.225 m, it results in the largest area of high turbulent kinetic energy. (iii) The number or spacing of dikes exhibits a negative correlation with the shape parameters of the separation and backflow behind the dikes, whereas there is a positive correlation between the angle of dikes and these shape parameters. (iv) Influenced by the deployment of dikes, novel helical flows will be generated around the dikes at the confluence. The helicity of the clockwise helical flow is comparatively smaller than that of its counterclockwise counterpart. Subsequently, newly generated helical flows undergo fusion and division as it progresses downstream.

Flow and noise control of a cylinder using grooves filled with porous material

In the present numerical study, we propose a new passive flow control mechanism at the Reynolds number of 3900. The novel method benefits from making grooves in the cylinder wall while the grooves are filled with porous materials of a specific permeability. According to the literature survey, while the porous medium is potentially an effective noise control method, it has serious drawbacks, mainly significant pressure drop. In the present study, instead of a porous coating, porous fillers are introduced offering substantial reduction of the noise level, in addition to managing the hydrodynamic parameters. To find a suitable design for the grooves and porous fillers, a systematic parametric study is performed on the number, sequence and size of the grooves, as well as the porous fillers' permeabilities. Based on the results, the newly proposed method dominated the traditional full porous coating by limiting the turbulent kinetic energy (TKE). The results of the parametric study indicated that grooves at an angle of 90° relative to the front stagnation point reduced the overall sound pressure level (OASPL) by 1.25 dB; meanwhile, the high-intensity TKE region shrunk. Further reductions were achieved by deeper grooves and porous fillers, as the drag coefficient, the lift coefficient, the Strouhal number, and the OASPL reduced up to 40.2%, 27.4%, 10.6%, and 3 dB, respectively. The proposed passive control method will be helpful for various industrial applications of cylinders through rigorous control of aerodynamic parameters and the noise level.

Energetic and dynamic characterization of pollutant dispersion in varied building layouts through an augmented analysis procedure

This work presents a post-data analysis procedure, namely, proper orthogonal decomposition (POD)–dynamic mode decomposition (DMD)–discrete Fourier transform analysis, for evaluating the dominant features of the flow fields from both energetic and dynamic perspectives. The large-eddy simulation (LES) was first employed to reproduce the flow field surrounding three types of building layouts. Subsequently, both POD and DMD were conducted according to LES simulation results. The extracted modes were classified into three types based on the POD and DMD: Type-1 mode: energetically and dynamically significant mode, Type-2 mode: energetically significant and dynamically insignificant mode, and Type-3 mode: energetically insignificant and dynamically significant mode. The findings indicate that Type-1 mode governs the primary velocity field and the predominant vortex patterns observed at the rear of the building arrays, as the reduction of inter-building widths leads to a shorter flow separation region. Type-2 mode is characterized by the presence of small-scale vortices and the high turbulent kinetic energy region, which periodically triggers pollutant increase in the vicinity of structures. Type-3 mode demonstrates a minimal energetic influence on the flow field; nevertheless, it significantly contributes to the consistent build-up of pollutants within the far-wake region. The present study also investigates the predominant coherent structures of flow fields concerning various building layouts and highlights the influence of passage widths on the efficiency of pollutant removal. This comprehensive analysis enables a systematic exploration of flow patterns within various building layouts, offering potential solutions for pollutant dispersion challenges in metropolitan areas.

Numerical investigation the shape of groove on tip leakage vortex suppression of a NACA0009 hydrofoil

To investigate the effect of different bionic grooves on the tip leakage vortex, four bionic grooves with different shapes were designed, which are semicircular, rectangular, triangular and trapezoid. The streamline, pressure, vortex strength and turbulence kinetic energy were analyzed to clarify the suppression mechanism. When the groove is arranged, the velocity of vortex center and the area of high-intensity vortex area decrease. The vortex strength in the triangular groove is higher than other groove shapes. The pressure in the center of the tip leakage vortex core increases. The low pressure area reduces obviously, which is the smallest in the trapezoidal groove condition. The turbulent kinetic energy in the main flow field increases, but decreases in the tip clearance. The high turbulent kinetic energy region is divided into small pieces by the bionic groove, which is the smallest in the rectangular groove condition. The bionic groove leads to the decrease in lift-to-drag ratio, which is the largest in the semicircular groove and smallest in the rectangular groove condition.

Vortex dynamics characteristics in the tip region based on Wray–Agarwal model

In order to solve the blockage effect and energy dissipation phenomenon caused by cavitation in the low-pressure vortex core region, this paper analyzes the spatial evolution of vorticity intensity and turbulent kinetic energy intensity under different cavitation conditions based on the Wray–Agarwal (WA) model. First, the tip leakage flow characteristics are studied, the evolution of vorticity and vorticity intensity is analyzed, then the distribution of turbulent kinetic energy distribution in the blade tip region is studied, and finally, the vorticity transport characteristics of the tip region are analyzed. It is found that the tip leakage rate is less affected by the vortex cavitation of the tip leakage, and there is a strong interaction between the leakage flow at the tip leading edge and the trailing edge, and the separation vortices and low-speed regions formed in the end-wall region cause blockage of the flow passage. Low pressure causes cavitation to cover most regions of the suction surface, inhibiting the formation and development of the tip leakage vortices. The distribution range of high turbulent kinetic energy region is almost the same as that of high-vorticity region, and there is a positive correlation between the two intensities. Severe cavitation causes the high turbulent kinetic energy region at the outlet of the flow passage to develop in the radial and axial directions of the impeller, which increases the turbulent dissipation and energy loss. The change of vorticity transport intensity caused by cavitation is mainly reflected in the expansion contraction term, and the Coriolis force term plays a dominant role in the vorticity transport process. This paper provides a reference for further improving the performance of mixed-flow pumps.

Reinforcement learning-based active flow control of oscillating cylinder for drag reduction

This study explores the use of a reinforcement learning (RL)-based active flow control strategy to reduce the drag of a transversely oscillating cylinder confined between two walls. We incorporate wake kinematic information of the oscillating cylinder from direct numerical solution into the agent to actively adjust the oscillating amplitude. Our findings reveal two strategies that significantly improve drag reduction. First, the oscillating frequency should be chosen within the lock-in region. Second, placing probes in the active region of turbulent kinetic energy enables the full utilization of physical information for achieving more efficient and stable control. The results show that an effective control strategy can reduce the drag by 8.4% compared to the case of stationary cylinder at Re = 200. We identify three characteristics of the controlled flow that contribute to drag reduction: an elongated recirculation zone, an increased energy transport coefficient, and asymmetric cylinder oscillation. We observed that this well-behaved controlled flow can be obtained through real-time RL-based control, as it consistently attenuates the asymmetric dynamic mode decomposition modes of the flow. Furthermore, we find that the asymmetry cylinder oscillation synchronizes with the vortex shedding, indicating that the RL-based control can expand the lock-in region.

Investigation of flow behavior in a refrigerator machine room using magnetic resonance velocimetry

This study aims to improve the energy efficiency and reduce flow noise in a refrigerator machine room by investigating the flow behavior using magnetic resonance velocimetry (MRV). A 1/2 scale model of the machine room was fabricated using stereolithography 3D printing, and the 3-dimensional mean velocity and turbulent kinetic energy (TKE) field were measured. Results from the reference model showed highly non-uniform flow distribution and high TKE regions. An improved machine room geometry was proposed, which led to an increase in mean flowrate through the condenser by 17.3% and a reduction in high TKE regions by over 77%, potentially resulting in improved energy efficiency and reduced turbulence-induced noise. These findings demonstrate the effectiveness of MRV in analyzing the flow behavior of complex 3D geometry such as the refrigerator machine rooms. The proposed improvements, including repositioning of flow-blocking pillars, relocating refrigerant pipes, changing inlet configurations, and increasing the area of inlet and outlet grilles, were validated using MRV. The results also confirm the accuracy of the MRV measurements, which were validated using an electromagnetic flowmeter. These findings have implications for the practical application of cooling systems and highlight the potential of MRV for future research in analyzing fan noise and applying MRV to models with built-in fans.

Heat Transfer Enhancement of Regenerative Cooling Channel with Pyramid Lattice Sandwich Structures

To meet the requirements of high heat transfer efficiency and light weight, the pyramid lattice structures are applied to the regenerative cooling design of scramjets. This study numerically investigates heat transfer and fluid flow characteristics of kerosene in a regenerative channel with pyramid lattice sandwich structures. At the same porosity, the maximum wall temperature of the pyramid lattice sandwich regenerative cooling channel decreases by 30%. With increased porosity, the cooling capacity of the pyramid regenerative cooling channel decreases gradually. The numerical results show that a complex secondary flow appears in the flow field in the pyramid lattice structures. In the downstream region of each strut, a spiral vortex is formed which accelerates the flow velocity approaching the wall with heat transfer enhancement. Because of the disturbing effect of the strut, a high turbulent kinetic energy region is formed in the upstream region of each strut and the heat transfer is enhanced. In general, the local heat transfer in the upstream region of the pyramid strut is better than that in the downstream region. For pyramid lattice structures, the cooling structures with high convective heat transfer and relatively low pressure drop can be obtained by optimization of the design parameters.

Effects of baffle on flow structure and cyclic variation in stirred tanks with Rushton turbine

In order to reveal the effect of baffles on flow structure and cyclic variation stirred by Rushton turbines, particle image velocimetry experiments were performed in baffled and unbaffled stirred tanks. In a baffled tank, the peak value of time-averaged velocity obviously increases, the high velocity region enlarges significantly, and the fluctuation of fluid elements near the turbine increases significantly. In the 20° phase plane of the baffled tank, the high swirl strength region slightly enlarges, but the peak of phase-resolved swirl strength is lower. The peak value and high value regions of turbulent kinetic energy are larger in the baffled stirred tank at various phase planes. Using quadruple proper orthogonal decomposition, the flow field is decomposed into a small-scale part, a transition part, a large-scale part, and a mean part with different spatial scales. Adding the baffle, the mean part with largest spatial scale obviously increases (it is favorable for mass transfer at different liquid levels) and the transition part, which mainly includes the random fluctuation of a turbulent cascade, slightly enhances (it is conducive to diffusion). The main influence of cyclic variation for various blade passages is the flow with large-scale, and the standard deviation of time coefficients decreases by 3%–4% for the mean part and the large-scale part by adding the baffle.

Dynamic Analysis of Wake Characteristics of the Circular Cylinder with a Dimpled Surface

In order to understand the wake characteristics for the circular cylinder with the dimpled structure, particle image velocimetry (PIV) and proper orthogonal decomposition (POD) method are used to measure and analyze the flow field velocity and the flow characteristic of the wake flow of the circular cylinder with the dimpled surface. This study focuses on the distribution of Reynolds stress and turbulent kinetic energy, the velocity profiles and recirculation zones, and the velocity fluctuating characteristics of flow field with POD technology. It is found that the equivalent high-intensity Reynolds stress and turbulent kinetic energy regions of the circular cylinder with the dimpled surface are smaller, and the peak values are lower, and the velocity gradient in the wake region of the circular cylinder with the dimpled surface is larger. Otherwise, the energy contained by the dominant modes of the smooth cylinder is larger than that contained by the dominant modes of the circular cylinders with the dimpled surface, which means the energy of the dimpled cylinder is more distributed. At the same time, it is observed that the dimpled structure will decrease the vortex shedding intensity, but may increase the vortex shedding frequency, and destroy the inherent flow mode of the flow field around the cylinder.

A numerical study of drag reduction performance of simplified shell surface microstructures

Antifouling and drag reduction are two critical issues for the shipping industry. Previous studies have revealed that biomimetic shell surfaces have distinct antifouling features. In this study, ten simplified surface microstructures with the same cross-section area are designed based on the antifouling scale of the shell surface morphology. Turbulent flow over the riblet structures is simulated using a finite volume based CFD solver with the Shear Stress Transport k-ω model to examine the effects of the riblet structures on skin friction with mean flow velocities ranging from 1 to 7 m/s. The corresponding dimensionless square root of the groove cross-section area is lg+≈4.5–25.6. Considering the predicted drag performance and issues concerning riblet tip rounding and fabrication, an optimal geometry with both antifouling and drag reduction features has been identified. The present study confirms that the riblets lift off streamwise vortices, pushing the high turbulent kinetic energy region away from the surface, and impede the spanwise movement of streamwise vortices, leading to skin-friction reduction. Further, the investigation of the effect of the riblet interval on the drag behaviour indicates the existence of a balance point between the wetted perimeter and the total area of the riblet surface for minimizing drag.

Effect of Furnace Gas Composition on Characteristics of Supersonic Oxygen Jets in the Converter Steelmaking Process.

During the converter steelmaking process, the presence of supersonic oxygen jets can provide oxygen to high-temperature metal baths that promotes chemical reactions in the bath, accelerates the smelting rhythm, and facilitates a uniform distribution of the ingredients in the bath. In this paper, a computational fluid dynamics (CFD) model with combustion reactions is established and compared to the results of combustion experiment. This paper studies the behavior and fluid flow characteristics of supersonic oxygen jets under different environmental compositions under a steelmaking temperature of 1873 K. This validated CFD model can be used to investigate the effect of furnace gas on supersonic oxygen jet characteristics during the converter steelmaking process. The results indicate that the composition of furnace gas has an impact on the characteristics of the oxygen jet. Specifically, as the carbon monoxide (CO) volume fraction increases, the high velocity region of supersonic oxygen jet increases, and the high temperature and the high turbulent kinetic energy regions expand.

Experiments on asymmetric vortex pair interaction with the ground

The interaction between the asymmetric vortex pair and the ground was experimentally investigated in a closed-circuit water channel for the current study. Particle image velocimetry tests were conducted to achieve the velocity measurements of flow fields at various crossflow planes. The vortex pair, with the reference circulation Reynolds number ReΓ ≈ 4490, was tested with various initial heights (h0/b0 = 1.5, 1.0 and 0.5) and circulation ratios (λ = 0.36:1, 1:0.36, 0.6:1, 1:0.6), with it being found that according to different interaction effects, the trajectory and merger of the vortex pair could be significantly affected. As the primary vortex pair approached the ground, a high turbulent kinetic energy region was observed between the secondary and primary vortical structures, which suggests violent interaction and accelerated circulation decay of the primary vortex. In addition, depending on the distribution of secondary vorticity and image vortices to the moving coordinate system, merging-promoting or -inhibiting effects were observed, which eventually affected the evolution of the primary vortex pair.

Numerical predictions of the flow characteristics of subsonic jet emanating from corrugated lobed nozzle

PurposeThe purpose of this study is to investigate the aerodynamic characteristics of subsonic jet emanating from corrugated lobed nozzle.Design/methodology/approachNumerical simulations of subsonic turbulent jets from corrugated lobed nozzles using shear stress transport k-ω turbulence model have been carried out. The analysis was carried out by varying parameters such as lobe length, lobe penetration and lobe count at a Mach number of 0.75. The numerical predictions of axial and radial variation of the mean axial velocity, u′u′ ¯ and v′v′ ¯ have been compared with experimental results of conventional round and chevron nozzles reported in the literature.FindingsThe centreline velocity at the exit of the corrugated lobed nozzle was found to be lower than the velocity at the outer edges of the nozzle. The predicted potential core length is lesser than the experimental results of the conventional round nozzle and hence the decay in centreline velocity is faster. The centreline velocity increases with the increase in lobe length and becomes more uniform at the exit. The potential core length increases with the increase in lobe count and decreases with the increase in lobe penetration. The turbulent kinetic energy region is narrower with early appearance of a stronger peak for higher lobe penetration. The centreline velocity degrades much faster in the corrugated nozzle than the chevron nozzle and the peak value of Reynolds stress appears in the vicinity of the nozzle exit.Practical implicationsThe corrugated lobed nozzles are used for enhancing mixing without the thrust penalty inducing better acoustic benefits.Originality/valueThe prominent features of the corrugated lobed nozzle were obtained from the extensive study of variation of flow characteristics for different lobe parameters after making comparison with round and chevron nozzle, which paved the way to the utilization of these nozzles for various applications.

Numerical Modeling of 3D Flow Field among a Compound Stilling Basin

Due to great velocity gradients among the outgoing flow, it is much common to form large-scale reverse flow with oblique movements outside the conventional separated stilling basin. Aimed at above problems, this paper proposes to remove the longitudinal splitter wall and then physically and numerically investigate the corresponding influence upon the compound stilling basin. The standard k-ε, renormalization group k-ε, realizable k-ε, and large eddy simulation turbulence models are all employed to reveal downstream three-dimensional flow field. Experimental validation of numerical results shows that the renormalization group k-ε turbulence model is the most successful in predicting the flow field among the four models. Both methods prove that the removed splitter wall exerts great impact upon downstream stilling basin. In view of the removed splitter wall, discharging inflow would greatly diffuse to form a typical three-dimensional (3D) hydraulic jump with large-scale reverse flow. High energy dissipation region and high turbulent kinetic energy region are both moved upstream. Thus, the velocity decay among the discharging flow in the compound stilling basin is significantly enhanced. Compared to the separated stilling basin, the maximum velocity and average velocity of the outgoing flow, respectively, decrease more than 30%, and 20% in the compound stilling basin. Additionally, the velocity gradients between the left and the right outgoing flow reduce by over 65% with turbulent kinetic energy gradients almost down to zero. The outgoing flow from the compound stilling basin becomes much uniform with the phenomenon of obliquely moving flow totally eliminated.

Calculation of cavitation evolution and associated turbulent kinetic energy transport around a NACA66 hydrofoil

The physical mechanism of flow unsteadiness is one of the key problems in cavitating flow. Significant efforts have been exerted to explain the cavitation-vortex interaction mechanism. As well, the process of kinetic energy transport during the evolution of unsteady cavitating flow must be elucidated. In this work, 2D calculations of cavitating flow around a NACA66 hydrofoil were performed based on the open source software OpenFOAM. The modified shear stress transport k-ω turbulence model, which considers curvature and turbulent eddy viscosity corrections, was employed to close the governing equations. The Schnerr-Sauer cavitation model was adopted to capture the cavitation phase change process. Numerical results showed reasonable consistency with the results of the experiments conducted by Leroux et al. (2004). The results showed that cavitation promotes turbulence intensity and flow unsteadiness around the hydrofoil. During the attached sheet cavity growth stage, high-value regions of turbulent kinetic energy are located substantially at the interface of the cavity, particularly at the rear portion of the cavity region. During the cloud cavity shed-off stage, the cavity begins to break off and the maximum value of turbulent kinetic energy is observed inside the shed cavity. Finally, the influence of cavitation on the turbulence intensity is illustrated using the turbulent kinetic energy transport equation, which shows that the pressure diffusion and turbulent transport terms dominate as cavitation occurs. In addition, cavitation promotes turbulence production and increases dissipation with fluid viscosity and flow unsteadiness. The viscous transport term only acts in the cavitation shedding stage under large-scale vortex shedding. Overall, these findings are of considerable interest in engineering applications.

Effects of the pocket cavity on heat transfer and fluid flow of the downstream outlet guide vane at different flow attacking angles

A pocket cavity is generated at the junction position of the low pressure turbine (LPT) and the outlet guide vane (OGV) in the rear part of a modern gas turbine jet engine. In the present study, a triangular pocket cavity is placed upstream of an OGV at different distances. The effects of the pocket cavity on heat transfer and fluid flow of the downstream OGV with different flow attack angles are investigated numerically with well validated turbulence models. The flow attack angles are varied as –30°, 0°, and +30° at a constant Reynolds number =160,000. The turbulent flow details are provided by numerical calculations using two turbulence models, the unsteady DES model and the steady k-ω SST model. For different flow attack angles, the high Nusselt number regions around the OGV are changed. The high heat transfer region is really drawn back at a flow attack angle = +30° (Case 2b) compared with Case 2a with a flow attack angle =0°. As the flow attack angle is changed to –30° (Case 2c), the high Nusselt number regions are greatly enlarged not only on the suction side also on the pressure side because of the strengthened flow impingement on the vane surfaces. The pocket cavity weakens the flow impingement on the vane surfaces and the effect is more obvious when the pocket cavity is placed close to the vane. In addition, the heat transfer distribution over the pocket surface is also affected by the location of the vane. When the vane is placed close to the pocket cavity (Case 1), the heat transfer on the pocket edge is increased. In the case with a flow attack angle =0°, the high turbulent kinetic energy region is mainly located near the vane and wake region downstream the vane and recirculating flows can hardly be found.

A tomographic-PIV investigation of vapor-induced flow structures in confined jet impingement boiling

Tomographic particle image velocimetry (PIV) is used to study the effect of confinement gap height on the liquid flow characteristics in jet impingement boiling. This first application of tomographic PIV to flow boiling is significant given the complexity of confined two-phase jet impingement. A jet of subcooled water at a Reynolds number of 5,000 impinges onto a circular heat source undergoing boiling heat transfer at a constant heat input. Confinement gap heights of 8, 4, and 2 jet diameters are investigated. A visual hull method is used to reconstruct the time-varying regions of the vapor in the flow. The vapor motion is found to govern the liquid flow pattern and turbulence generation in the confinement gap. Time-averaged velocities and regions of turbulent kinetic energy in the liquid are highest for a confinement gap height of 8 jet diameters, with lower velocity magnitude and turbulence being observed for the smaller spacings. Coherent vortical structures identified with the λ2-criterion are found to occur most frequently near the moving vapor interface. The most intense regions of turbulent kinetic energy do not coincide with the location of coherent structures within the flow. Irrotational velocity fluctuations in the liquid phase caused by vapor bubble pinch-off are the primary cause of the high turbulent kinetic energy measured in these regions. At a gap height of H/d=2 the vapor plume is constrained as it grows from the heat source, causing bulk flow oscillations in the downstream region of the confinement gap.

Hemodynamics of the Boston Scientific Lotus™ Valve: An In Vitro Study

Transcatheter Aortic Valve Replacement (TAVR) is currently used for patients with aortic valve disease at high risk for surgical intervention. The Lotus™ Valve system (Boston Scientific) is a novel repositionable TAVR with bovine pericardial leaflets and a Nitinol® frame, including miniature buckles for repositioning. A detailed characterization of the fluid flow environment in the vicinity of the buckles and the sinus regions will help identify regions of potential flow stagnation and thrombosis. A Lotus Valve was deployed in an in vitro left heart simulator, and the fluid flow through the valve was quantitatively characterized using particle image velocimetry. Three planes of high spatial resolution velocity data were obtained across the valve through the entire cardiac cycle at three stroke volumes (SV). The resulting velocity fields were processed to obtain Reynolds shear stresses (RSS), viscous shear stresses (VSS) and turbulent kinetic energy (TKE) fields. The Lotus Valve showed a central systolic jet at all three SV in the central plane. This jet caused a strong sinus vortex, which persisted through entire systole for all three SV. The location of the vortex was dependent on the SV through the valve. High VSS, RSS and TKE regions were observed at the edge of the systolic jet distal to the valve, however high velocities in these regions caused washout of fluid, which may prevent thrombus formation. The buckle region did not appear to significantly increase the potential for hemolysis of this valve. The Lotus Valve showed very good hemodynamic performance and no regions of stagnation were observed in the vicinity of the valve. These results compare favorably with flow characteristics through bioprosthetic aortic valve replacements, and suggest good clinical performance with this valve system.